U.S. patent application number 11/102778 was filed with the patent office on 2005-09-01 for film and adhesive therefor.
This patent application is currently assigned to BRIDGESTONE CORPORATION. Invention is credited to Kitano, Hideki, Kotsubo, Hidefumi, Murayama, Kenji, Sasaki, Kiyomi.
Application Number | 20050191485 11/102778 |
Document ID | / |
Family ID | 32110953 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050191485 |
Kind Code |
A1 |
Kitano, Hideki ; et
al. |
September 1, 2005 |
Film and adhesive therefor
Abstract
An adhesion-including film is provided, wherein the total light
transmittance is varied in a width direction of the film. The
adhesion-including film includes a mold release film, a first
adhesive layer disposed on this mold release film, a second
adhesive layer disposed on the first adhesive layer, a base film on
the second adhesive layer, and an antireflection film disposed on
the film surface opposite to the second adhesive layer of the base
film. The first adhesive layer is highly colored as compared with
the second adhesive layer. The second adhesive layer may be
colorless. The thickness of the central portion of the first
adhesive layer in the width direction of the film is larger than
the thicknesses of both end sides. The total thickness of the first
adhesive layer and the second adhesive layer is uniform all over
the film.
Inventors: |
Kitano, Hideki;
(Kodaira-shi, JP) ; Sasaki, Kiyomi; (Kodaira-shi,
JP) ; Murayama, Kenji; (Kodaira-shi, JP) ;
Kotsubo, Hidefumi; (Kodaira-shi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
BRIDGESTONE CORPORATION
|
Family ID: |
32110953 |
Appl. No.: |
11/102778 |
Filed: |
April 11, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11102778 |
Apr 11, 2005 |
|
|
|
PCT/JP03/12876 |
Oct 8, 2003 |
|
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Current U.S.
Class: |
428/343 ;
428/354; 428/355AC |
Current CPC
Class: |
G03B 17/26 20130101;
C09J 2433/00 20130101; B32B 2307/40 20130101; G02B 5/22 20130101;
B32B 7/10 20130101; C09J 7/22 20180101; G02B 5/20 20130101; C09J
7/38 20180101; C09J 133/06 20130101; Y10T 428/2848 20150115; B32B
2309/105 20130101; B32B 2457/20 20130101; B32B 2307/402 20130101;
Y10T 428/2891 20150115; C09J 7/29 20180101; C09J 2301/208 20200801;
C09J 2301/162 20200801; B32B 7/12 20130101; B32B 2551/00 20130101;
C09J 2301/302 20200801; Y10T 428/28 20150115 |
Class at
Publication: |
428/343 ;
428/354; 428/355.0AC |
International
Class: |
B32B 007/12; G03B
017/26 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2002 |
JP |
2002-303350 |
Oct 17, 2002 |
JP |
2002-303351 |
Jan 10, 2003 |
JP |
2003-004721 |
Sep 3, 2003 |
JP |
2003-311574 |
Claims
What is claimed is:
1. A film having a light transmission property, wherein the total
light transmittance is varied in a transverse direction of the
film.
2. The film according to claim 1, wherein the total light
transmittance of the central portion in the transverse direction of
the film is lower than those of both end sides.
3. The film according to claim 1, wherein the distribution of the
total light transmittance in the direction orthogonal to the
transverse direction of the film is uniform.
4. The film according to claim 1, wherein the total light
transmittance is varied periodically in the direction orthogonal to
the transverse direction of the film.
5. The film according to claim 1, comprising a base film and an
adhesive layer disposed on the base film.
6. The film according to claim 5, wherein the adhesive layer is a
colored layer.
7. The film according to claim 6, wherein the total light
transmittance is varied with changes in the thickness of the
adhesive layer.
8. The film according to claim 6, wherein the total light
transmittance is varied with changes in the color strength of the
adhesive layer.
9. An adhesive-including film according to claim 5, wherein the
adhesive layer comprises a colored first adhesive layer and a
colorless or light-colored second adhesive layer, the second
adhesive layer being light-colored as compared with the first
adhesive layer, and the total light transmittance is varied with
changes in the thickness of the first adhesive layer.
10. The adhesive-including film according to claim 9, wherein the
total thickness of the first adhesive layer and the second adhesive
layer is uniform all over the film.
11. The film according to claim 1, wherein the film is a colored
base film.
12. The film according to claim 5, wherein the total light
transmittance is varied with changes in the thickness of the base
film.
13. The film according to claim 5, wherein the total light
transmittance is varied with changes in the color strength of the
base film.
14. The film according to claim 1, comprising a base film and a
colored layer disposed on the base film, wherein the total light
transmittance of the film having a light transmission property is
varied with changes in the total light transmittance of the colored
layer.
15. The film according to claim 14, wherein the total light
transmittance of the film having a light transmission property is
varied with changes in the thickness of the colored layer.
16. The film according to claim 14, wherein the total light
transmittance of the film having a light transmission property is
varied with changes in the color strength of the colored layer.
17. The film according to claim 14, wherein the colored layer is a
printed layer.
18. The film according to claim 14, wherein the colored layer is a
part of an antireflection layer, a hard coat layer, an antiglare
layer, or an electrically conductive layer.
19. A method for manufacturing an adhesive-including film,
including the step of supplying an adhesive on a film surface to
form an adhesive layer on the film surface while the film is
continuously forwarded, the method comprising the step of: forming
the adhesive layer so that the thickness of the adhesive layer is
varied in a film width direction orthogonal to the forwarding
direction of the film.
20. The method for manufacturing an adhesive-including film
according to claim 19, comprising the step of: forming the adhesive
layer by leveling the adhesive on the film surface with a blade,
wherein the clearance between the blade and the film surface is
varied in the width direction.
21. The method for manufacturing an adhesive-including film
according to claim 20, wherein the clearance between the blade and
the film surface is periodically varied with time.
22. The method for manufacturing an adhesive-including film
according to claim 21, wherein the clearance between the blade and
the film surface is periodically varied with time by shaking the
blade in the forwarding direction of the film.
23. A dimmer film including a base film, a colored layer disposed
on the base film, and an adhesive layer disposed on the colored
layer and having a light transmission property with a total light
transmittance being varied in a surface direction due to changes in
the color strength of the colored layer in the surface direction,
wherein the colored layer contains a heat-resistant dye readily
fading due to ultraviolet light B, the colored layer has been faded
by being irradiated with the ultraviolet light B having a light
quantity distribution in the surface direction so that the color
strength is varied in the surface direction, and the adhesive layer
contains a pigment.
24. A method for manufacturing a dimmer film including a base film,
a colored layer disposed on the base film, and an adhesive layer
disposed on the colored layer and having a light transmission
property with a total light transmittance being varied in a surface
direction of the film, the method comprising the steps of: forming
the colored layer on a substrate, the colored layer containing a
heat-resistant dye readily fading due to ultraviolet light B, in a
first step; irradiating the colored layer with the ultraviolet
light B through a mask having an ultraviolet light B transmission
quantity distribution in the surface direction so that the colored
layer is faded and the color strength is varied in the surface
direction, in a second step; and thereafter, forming the adhesive
layer on the colored layer, the adhesive layer containing a
pigment, in a third step.
25. The method for manufacturing a dimmer film according to claim
24, wherein the mask comprises a polyethylene terephthalate film
and exhibits the light transmission quantity distribution due to
changes in the thickness in the surface direction.
26. The method for manufacturing a dimmer film according to claim
24, wherein the colored layer is a colored adhesive layer.
27. The method for manufacturing a dimmer film according to claim
24, wherein the total light transmittance of the central portion in
the transverse direction of the dimmer film is lower than those of
both end sides.
28. The method for manufacturing a dimmer film according to claim
24, wherein the distribution of total light transmittance in the
direction orthogonal to the transverse direction of the dimmer film
is uniform.
29. The method for manufacturing a dimmer film according to claim
24, wherein the total light transmittance is varied in the
direction orthogonal to the transverse direction of the dimmer
film.
30. The method for manufacturing a dimmer film according to claim
24, wherein the colored layer is formed by gravure coating.
31. The method for manufacturing a dimmer film according to claim
24, wherein the colored layer is a part of an antireflection layer,
a hard coat layer, an antiglare layer, or an electrically
conductive layer.
32. A dimmer film manufactured by the method for manufacturing a
dimmer film according to claim 24.
33. A display adhesive comprising a (meth)acrylic resin as a
primary component and a cross-linking agent, wherein the
(meth)acrylic resin contains 1 to 25 percent by weight of monomer
component having a carboxyl group, as a copolymerization component
of the alkyl (meth)acrylate, and the cross-linking agent is an
epoxy compound.
34. The display adhesive according to claim 33, wherein the weight
average molecular weight of the (meth)acrylic resin is 500,000 to
2,000,000.
35. The display adhesive according to claim 33, wherein the monomer
component having a carboxyl group is at least one selected from the
group consisting of (meth)acrylic acid, carboxyethyl(meth)acrylate,
carboxypentyl(meth)acrylate, itaconic acid, maleic acid, and
crotonic acid.
36. The display adhesive according to claim 33, wherein the content
of the cross-linking agent is 0.5 to 50 percent by weight relative
to the monomer component having a carboxyl group.
37. A display functional film, in which an adhesive layer
comprising the display adhesive according to claim 33 is disposed
on one surface of a base film.
38. The display functional film according to claim 37, wherein at
least one selected from the group consisting of a hard coat layer,
a transparent electrically conductive layer, an antiglare layer,
and an antireflection layer is disposed on the other surface of the
base film.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a continuation application of PCT/JP03/12876 filed
on Oct. 8, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] I. An aspect of the present invention relates to a film and
a method for manufacturing the film. In particular, it relates to a
film suitable for electronic displays, e.g., liquid crystal
displays, and to a method for manufacturing the film.
[0004] II. Another aspect of the present invention relates to a
dimmer film and a method for manufacturing the dimmer film. In
particular, it relates to a dimmer film suitable for electronic
displays, e.g., liquid crystal displays, and having a light
transmission property with the total light transmittance being
varied in a surface direction, and to a method for manufacturing
the dimmer film.
[0005] III. Another aspect of the present invention relates to an
adhesive to stick a functional film, e.g., an antireflection film,
on a front panel of a display, e.g., a plasma display or a liquid
crystal display, and to a functional film provided with an adhesive
layer made of this adhesive. In particular, it relates to a display
adhesive exhibiting high adhesion to a display panel and having the
adhesion and optical properties exhibiting excellent
high-temperature durability and high-humidity durability and to a
display functional film.
[0006] 2. Description of the Related Art
[0007] I. Light sources are required to display letters and images
on liquid crystal displays. In recent years, thicknesses of
displays have been reduced. Consequently, the light from the light
source is incident from one side surface or two side surfaces. Now,
the light is scattered by using a light guide plate, a diffusion
film, and the like so that the light reaches the front of the
display panel.
[0008] In order to prevent damage to the display panel and improve
viewability, a functional light transmission film is stuck on a
front panel. An adhesive is adhered to this film, and the film is
stuck by this adhesive layer (for example, Japanese Unexamined
Patent Application Publication No. 2002-107507).
[0009] The uniformity of the luminance of the display panel is not
perfect, and variations in luminance may occur. In particular, as
the display is upsized, variations in luminance tend to become
conspicuous. As for the above-described variations in luminance, in
general, the luminance is decreased with distance from the light
source. However, sometimes, the luminance is decreased as the light
source approaches, or is varied, such as dark-bright-dark,
depending on the configuration of the light guide plate. In many
cases, variations in luminance are generally in such a manner that
the luminance is varied in a direction of a straight line. In some
type of display, a phenomenon occurs, in which the luminance of the
central portion of a screen is high, but the luminance of the
perimeter is low.
[0010] II. Various functional light transmission films, e.g., a
film provided with a hard coat layer, a transparent electrically
conductive layer, an antiglare layer, an antireflection layer, and
the like on one surface of a light transmission film, are attached
to front panels (display panels) of various electronic displays,
e.g., plasma displays and liquid crystal displays, for the purpose
of providing functionality, e.g., antireflection property and
antiglare property.
[0011] In general, various electronic display panels are composed
of hard sheets, e.g., glass sheets, acrylic sheets, and
polycarbonate sheets, having thicknesses of about 1 to 10 mm.
Functional light transmission films, e.g., antireflection films,
are stuck to these various electronic display panels with
adhesives.
[0012] Various adhesives of, e.g., rubber base, acryl base, and
silicone base, have been previously provided as the adhesives used
for sticking these functional light transmission films in
accordance with the material systems. Among them, acrylic adhesives
are most suitable as display adhesives required to have high
optical performances.
[0013] However, with respect to known acrylic adhesives, there is a
problem of reduction in adhesion or deterioration, e.g., yellowing,
under a specific use environment. That is, for example, there are
problems of peeling of a functional light transmission film due to
reduction in adhesion and deterioration of transparency due to
yellowing of the adhesive because of a high humidity condition, an
occurrence of an external factor of heating, or an occurrence of
abnormal internal heat generation.
SUMMARY OF THE INVENTION
[0014] I. It is a first object of the present invention to provide
a light transmission film capable of overcoming the above-described
problems in the background art I and eliminating or suppressing
variations in luminance of a display panel, as well as a method for
manufacturing the same.
[0015] A light transmission film according to an aspect of the
present invention is characterized in that the total light
transmittance is varied in a transverse direction of the film.
[0016] This film can exhibit a distribution of light and dark which
is the reverse of high and low of the luminance in accordance with
variations in luminance of the display. This film is stuck to the
display and, thereby, variations in luminance of the display can be
eliminated or suppressed.
[0017] The total light transmittance of the film may be varied not
only in the transverse direction, but also in the direction
orthogonal to the transverse direction. That is, the total light
transmittance may be varied not only in a one-dimensional
direction, but also in a two-dimensional direction.
[0018] In order to vary the total light transmittance of the film
in a one-dimensional direction or a two-dimensional direction, in
the case where the film includes a base film and a colored adhesive
layer, the total light transmittance of this adhesive layer may be
varied in a one-dimensional direction or a two-dimensional
direction. The total light transmittance of the adhesive layer can
be varied in a one-dimensional direction or a two-dimensional
direction by changes in the thickness or the color strength of the
adhesive layer.
[0019] The total light transmittance of the film can also be varied
in a one-dimensional direction or a two-dimensional direction by
forming a colored layer other than the adhesive layer on the base
film and changing the thickness or the color strength of this
colored layer. This colored layer may be a functional layer, e.g.,
an antireflection layer, a hard coat layer, an antiglare layer, or
an electrically conductive layer. The color may be either a
chromatic color or an achromatic color.
[0020] In the case where the base film itself which constitutes the
film is colored, the total light transmittance of the film may be
varied in a one-dimensional direction or a two-dimensional
direction by changing the thickness or the color strength of this
base film.
[0021] This film can be used not only for liquid crystal displays
of back light system or front light system, but also for other
displays, e.g., CRT, PDP, and FED. This film can also be used for
display panels, e.g., electric bulletin boards, having light
sources.
[0022] According to another aspect of the present invention, a
method for manufacturing an adhesive-including film, including the
step of supplying an adhesive on a film surface to form an adhesive
layer on the film surface while the film is continuously forwarded,
is provided. The method includes the step of forming the adhesive
layer so that the thickness of the adhesive layer is varied in a
film width direction orthogonal to the forwarding direction of the
film.
[0023] A method in which all materials are homogeneously mixed,
kneading is performed with an extruder, rolls, or the like and,
thereafter, a film in a predetermined shape is formed by a film
formation method, e.g., calender rolling, T die extrusion, or
inflation, can be used as the method for forming (a film of) an
adhesive layer on a film. For example, in the T die extrusion, the
thickness of the formed film is varied in one direction (transverse
direction) by changing the thickness of an extrusion hole.
Consequently, the total light transmittance is varied. In addition,
a film can also be formed by a method in which all constituents are
homogeneously mixed and dissolved into a good solvent, the
resulting solution is applied to a support, a separator made of a
precise coating of silicone or fluororesin, by a flow coating
method, a roll coating method, a gravure roll method, a meyer bar
method, a lip die coating method, or a comma method, and the
solvent is removed by drying. At that time, in order to change the
thickness of the formed film in a direction perpendicular to the
coating direction, for example, in the comma method, a gap between
a roll and a knife is changed in the perpendicular direction by
providing curving. Consequently, the thickness after drying is
varied.
[0024] II. It is a second object of the present invention to
provide a dimmer film capable of overcoming the above-described
problems in the background art I and having a light transmission
property with the total light transmittance being varied in a
surface direction, wherein a desired transmitted color can be
readily attained, as well as a method for manufacturing the
same.
[0025] A dimmer film according to another aspect of the present
invention includes a base film, a colored layer disposed on the
base film, and an adhesive layer disposed on the colored layer and
has a light transmission property with the total light
transmittance being varied in a surface direction due to changes in
the color strength of the colored layer in the surface direction,
wherein the colored layer contains a heat-resistant dye readily
fading due to ultraviolet light B, the colored layer has been faded
by being irradiated with the ultraviolet light B having a light
quantity distribution in the surface direction so that the color
strength is varied in the surface direction, and the adhesive layer
contains a pigment.
[0026] A method for manufacturing a dimmer film including a base
film, a colored layer disposed on the base film, and an adhesive
layer disposed on the colored layer and having a light transmission
property with the total light transmittance being varied in a
surface direction of the film, according to another aspect of the
present invention, includes the steps of forming the colored layer
on a substrate, the colored layer containing a heat-resistant dye
readily fading due to ultraviolet light B, in a first step;
irradiating the colored layer with the ultraviolet light B through
a mask having an ultraviolet light B transmission quantity
distribution in the surface direction so that the colored layer is
faded and the color strength is varied in the surface direction, in
a second step; and thereafter, forming the adhesive layer on the
colored layer, the adhesive layer containing a pigment, in a third
step.
[0027] The dimmer film having the total light transmittance being
varied in a surface direction can be produced by irradiating the
colored layer with the ultraviolet light B having a light quantity
distribution in the surface direction so that the colored layer is
faded and the color strength is varied in the surface direction,
the colored layer containing a heat-resistant dye readily fading
due to the ultraviolet light B. Since the adhesive layer containing
the pigment is formed on this colored layer, the transmitted color
of the dimmer film can be arbitrarily adjusted to become a desired
color tone by the pigment in the adhesive layer.
[0028] The dimmer film having the total light transmittance being
varied in a surface direction may be produced by only a colored
layer having the color strength being varied in the surface
direction. However, in this case, the transmitted color of the
dimmer film becomes equal to the transmitted color of the base film
depending on the degree of fading of the colored layer, and it is
difficult to attain a desired transmitted color. In the present
invention, since the adhesive layer containing a pigment is
disposed on this colored layer, the transmitted color of the dimmer
film can be arbitrarily adjusted to a desired color tone.
[0029] In the present invention, preferably, the mask having an
ultraviolet light B transmission quantity distribution in the
surface direction is made of a polyethylene terephthalate (PET)
film, and has the ultraviolet light B transmission quantity
distribution due to changes of the thickness in the surface
direction.
[0030] Preferably, the colored layer is a colored adhesive layer.
The colored layer may be a part of an antireflection layer, a hard
coat layer, an antiglare layer, or an electrically conductive
layer. Preferably, the colored layer is formed by gravure
coating.
[0031] In the dimmer film according to an aspect of the present
invention and the dimmer film manufactured by the method according
to another aspect of the present invention, the total light
transmittance of the central portion in the transverse direction of
the dimmer film may be lower than those of both end sides, and the
distribution of the total light transmittance in the direction
orthogonal to the transverse direction of the dimmer film may be
uniform.
[0032] In the dimmer film, the total light transmittance may be
varied in the direction orthogonal to the transverse direction of
the dimmer film.
[0033] According to the dimmer film of the present invention and
the manufacturing method therefor, a dimmer film having a light
transmission property with the total light transmittance being
varied in a surface direction and a desired transmitted color can
be readily attained.
[0034] III. It is a third object of the present invention to
provide a display adhesive capable of overcoming the
above-described problems in the background art II and having high
adhesion to various display panels while the adhesion and optical
properties exhibit excellent high-temperature durability and
high-humidity durability, as well as a display functional film
including this adhesive.
[0035] A display adhesive according to another aspect of the
present invention contains a (meth)acrylic resin as a primary
component and a cross-linking agent, wherein the (meth)acrylic
resin contains 1 to 25 percent by weight of monomer component
having a carboxyl group, as a copolymerization component of the
alkyl(meth)acrylate, and the cross-linking agent is an epoxy
compound.
[0036] The term "(meth)acrylic" refers to "acrylic and/or
methacrylic", and the term "(meth)acrylate" refers to "acrylate
and/or methacrylate".
[0037] This adhesive has high adhesion, excellent heat resistance,
and excellent humidity resistance since a primary component is the
(meth)acrylic resin containing the monomer component having a
carboxyl group, and the cross-linking agent is contained.
Furthermore, the cross-linking agent is the epoxy compound having
very high thermal stability and, thereby, significantly high effect
is exerted on improvement of the heat resistance.
[0038] Preferably, the weight average molecular weight of the
(meth)acrylic resin is 500,000 to 2,000,000. Preferably, the
monomer component having a carboxyl group is at least one selected
from the group consisting of (meth)acrylic acid,
carboxyethyl(meth)acrylate, carboxypentyl(meth)acrylate, itaconic
acid, maleic acid, and crotonic acid. Preferably, the content of
the cross-linking agent is 0.5 to 50 percent by weight relative to
the above-described monomer component having a carboxyl group.
[0039] A display functional film according to another aspect of the
present invention include an adhesive layer on one surface of a
base film, the adhesive layer being made of the display adhesive
according to the above-described aspect of the present invention.
The display functional film has high adhesion to display panels and
excellent optical properties, each exhibiting excellent
high-temperature durability and high-humidity durability.
[0040] In this display functional film, usually, at least one
selected from the group consisting of a hard coat layer, a
transparent electrically conductive layer, an antiglare layer, and
an antireflection layer is disposed on the other surface of the
base film.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a sectional view of an adhesive-including film
according to an embodiment.
[0042] FIGS. 2A and 2B are sectional views showing a method for
manufacturing an adhesive-including film according to an
embodiment.
[0043] FIG. 3 is a sectional view showing a method for
manufacturing an adhesive-including film according to an
embodiment.
[0044] FIG. 4A is a sectional view showing a method for
manufacturing an adhesive-including film according to an
embodiment, and FIG. 4B is a diagram showing the shape of a
blade.
[0045] FIG. 5 is a perspective view showing a method for
manufacturing an adhesive-including film according to an
embodiment.
[0046] FIG. 6 is a sectional view showing a method for
manufacturing an adhesive-including film according to an
embodiment.
[0047] FIG. 7 is a sectional view showing a method for
manufacturing an adhesive-including film according to an
embodiment.
[0048] FIG. 8A is a vertical sectional view showing a method for
manufacturing an adhesive-including film according to another
embodiment. FIG. 8B is a sectional view of the section indicated by
a line VIIIb-VIIIb shown in FIG. 8A. FIG. 8C is a sectional view of
the section indicated by a line VIIIc-VIIIc shown in FIG. 8B.
[0049] FIGS. 9A to 9E are sectional views showing an embodiment of
a method for manufacturing a dimmer film according to the present
invention.
[0050] FIG. 10 is a sectional view showing an embodiment of a
display functional film according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0051] I. Embodiment will be described below with reference to the
drawings. FIG. 1 is a sectional view in the film width direction of
an adhesive-including film according to an embodiment. FIG. 2 to
FIG. 8C are explanatory diagrams of manufacturing methods
therefor.
[0052] This adhesive-including film 1 includes a mold release film
2, a first adhesive layer 3 disposed on this mold release film 2, a
second adhesive layer 4 disposed on the first adhesive layer, a
base film 5 on the second adhesive layer, and an antireflection
film 6 disposed on the film surface opposite to the second adhesive
layer 4 of the base film 5.
[0053] In the present embodiment, the first adhesive layer 3 is
highly colored as compared with the second adhesive layer 4. The
second adhesive layer 4 may be colorless. The thickness of the
first adhesive layer 3 is varied in the width direction of the film
1. In the present embodiment, the thickness of the central portion
of the first adhesive layer 3 in the width direction of the film is
larger than the thicknesses of both end sides. The total thickness
of the first adhesive layer 3 and the second adhesive layer 4 is
uniform all over the film.
[0054] In the case where the uniformity of the thickness of the
adhesive layer is unnecessary, the second adhesive layer may not be
disposed.
[0055] The film 1 is long-extended in a direction orthogonal to the
width direction (direction perpendicular to the drawing in FIG. 1).
The thickness of the first adhesive layer 3 may be uniform or
periodically changed in the longitudinal direction of the film.
[0056] A method for manufacturing this first adhesive layer 3 on a
mold release film will be described with reference to FIG. 4 to
FIG. 7.
[0057] As shown in FIG. 4A, the mold release film 2 is looped over
an application roll 10 and is forwarded continuously. The direction
of the center of axis of this application roll 10 is set in the
horizontal direction. A liquid dam 11 is disposed adjacent to this
application roll 10, and a coating solution 12 held in the liquid
dam 11 is in contact with the film surface of the mold release film
2.
[0058] As the film 2 is forwarded, the coating solution 12 is
adhered to the film surface and is pulled up. The coating solution
12 pulled up while being adhered to this film 2 is scraped and
leveled with a blade 13, so that the first adhesive layer 3 is
formed.
[0059] This blade 13 is attached to a comma 14. In the present
embodiment, as shown in FIG. 4B, the lower edge of the blade 13 has
the form of an arch surface 13a curved to become convex upward in
the width direction of the film 2. Consequently, the clearance
between the blade 13 and the film 12 reaches a maximum value at the
central portion of the width direction of the film 2 and decreases
with increasing proximity to both end sides of the film 2. Since
the coating solution 12 on the film 2 is leveled with this blade
13, the thickness of the adhesive layer 3 disposed on the film 2
reaches a maximum at the central portion in the width direction of
the film 2 and decreases with increasing proximity to both end
sides.
[0060] In order to complete the film 1, the second adhesive layer 4
may be formed on the first adhesive layer 3, as shown in FIGS. 2A
and 2B, and the base film 5 may be stacked thereon. Alternatively,
the second adhesive layer 4 may be formed on the base film 5, and
the mold release film 2 provided with the first adhesive layer 3
and the base film 5 provided with the second adhesive layer 4 may
be stacked, as shown in FIG. 3. The thickness of the second
adhesive layer 4 shown in FIG. 3 decreases with increasing
proximity to the central portion in the width direction of the film
5. The above-described second adhesive layer 4 may be formed on the
film 5 by using a blade curved to become convex downward, for
example.
[0061] As described above, the first adhesive layer 3 of the film 1
is highly colored as compared with the second adhesive layer 4.
Therefore, the film 1 is most highly colored (the total light
transmittance is low.) at the central portion in the width
direction, and becomes lightly colored with increasing proximity to
both end sides. That is, the total light transmittance of the film
1 is increased with increasing proximity to both end sides in the
width direction.
[0062] Consequently, in the case where the mold release film 2 is
peeled off and the film 1 is stuck to a display, when variations in
luminance of the display is in a pattern reverse to the
distribution of light and dark of the film 1, the variations in
luminance can be eliminated or reduced.
[0063] By making the blade 13 stand still as shown in FIG. 6, the
thickness of the first adhesive layer 3 is made uniform in the
longitudinal direction of the film 2. By shaking the blade 13 in
the direction indicated by an arrow .theta. as shown in FIG. 7, the
thickness of the first adhesive layer 3 is periodically varied in
the longitudinal direction of the film 2. In the case where the
configuration shown in FIG. 7 is adopted, an adhesive-including
film, in which dark and light are periodically varied not only in
the width direction of the film 1, but also in the direction
orthogonal thereto, is produced.
[0064] In FIG. 7, the lower edge side of the blade 13 is shaken.
However, the thickness of the first adhesive layer 3 can also be
periodically varied in the longitudinal direction of the film 2 by
shaking the upper edge side of the blade 13. The thickness of the
first adhesive layer 3 can also be periodically varied in the
longitudinal direction of the film 2 by periodically moving the
blade 3 up or down.
[0065] Although the blade is used in FIG. 7, the thickness of the
first adhesive layer 3 may also be varied in the longitudinal
direction of the film 2 by using a lip die 20 as shown in FIG. 8A.
The lips 21 of this lip die 20 have a large width of the opening at
the center in the width direction, and the width of the opening
decreases with increasing proximity to both end sides in the width
direction, as shown in FIG. 8B. In this manner, as shown in FIG.
8C, the thickness of the first adhesive layer 3 reaches a maximum
at the center in the width direction, and the thickness decreases
with increasing proximity to both end sides.
[0066] In the cases shown in FIGS. 8A to 8C, when the quantity of
discharge of the coating solution from the lip die 20 is made
constant with time, the thickness of the adhesive layer 3 becomes
uniform in the forwarding direction of the film 2. When the
above-described quantity is periodically increased and decreased,
the thickness is periodically varied in the forwarding
direction.
[0067] The thickness distribution of the adhesive layer 3 in the
film width direction in the above-described embodiment is an
example of aspects of the present invention, and the thickness
distribution is not limited to this. For example, the thickness of
the adhesive layer 3 may also be periodically varied in the film
width direction.
[0068] According to the present invention, a film exhibiting a
percentage a/b.times.100% of the total light transmittance a at the
center in the film width direction relative to the total light
transmittance b on both end sides of about 10% to 95% can be
provided. In the case where the total light transmittance is made
uniform in the longitudinal direction of the film, the rate of
change of the total light transmittance in the longitudinal
direction of the film can be made 10% or less.
[0069] In the case where the total light transmittance is
periodically varied in the longitudinal direction of the film, a
film exhibiting a percentage c/d.times.100% of the lowest total
light transmittance c at the center in the film width direction
relative to the highest total light transmittance d of about 20% to
95% can be provided.
[0070] The materials and thicknesses of the mold release film 2,
the adhesive layers 3 and 4, the base film 5, and the
antireflection film 6 are not specifically limited. For example,
the thickness of the mold release film 2 is 25 to 100 .mu.m, the
total thickness of the first adhesive layer 3 and the second
adhesive layer 4 is 20 to 40 .mu.m, the thickness of the base film
5 is 30 to 250 .mu.m, and the thickness of the antireflection film
6 is 0.1 to 10 .mu.m. However, the present invention is not
specifically limited to them. The thickness of the central portion
of the first adhesive layer 3 may be set at about 1.2 to 3 times
the thickness of both end sides, although not limited to this. The
colors of the adhesive layers 3 and 4 are not specifically limited.
The width of the film 1 is set at, for example, 500 to 1,000 mm,
although not limited to this.
[0071] Previously known various adhesives of, e.g., rubber base,
acryl base, silicone base, and EVA base, can be used as the
adhesive. A coloring matter added to the adhesive to adjust the
total light transmittance of the adhesive layer is not specifically
limited. Examples of pigments include inorganic pigments, e.g.,
carbon black, titanium oxide, chromium oxide, oxide yellow, red ion
oxide, and ultramarine, and organic pigments, e.g., azo pigments,
phthalocyanine pigments, anthracene pigments, threne pigments, and
dioxazine pigments, although not limited to them.
[0072] An example of adhesives suitable for use in the film of the
present invention is an adhesive containing a (meth)acrylic resin
as a primary component and an epoxy compound as a cross-linking
agent, wherein the (meth)acrylic resin contains 1 to 25 percent by
weight of monomer component having a carboxyl group, as a
copolymerization component of the alkyl(meth)acrylate.
[0073] This suitable adhesive is the same as that of the adhesive
layer 73 shown in FIG. 10 which will be described below.
[0074] Next, the materials for the mold release film 2 and the base
film 5 will be described.
[0075] Examples of materials for these films 2 and 5 include
cellulose films of triacetyl cellulose base, polycarbonate films,
polyester films, e.g., polyethylene terephthalate, and polyolefin
films, e.g., polyethylene and polypropylene, although not limited
to them.
[0076] The film 1 of the present invention may include at least one
of a hard coat layer, an electrically conductive layer, an
antireflection layer, an antiglare layer, and the like.
[0077] The adhesive-including film in accordance with the present
invention may be manufactured by mixing at least two formulations
having different total light transmittances and applying the
resulting mixture to a film immediately after the mixing so as to
form (a film of) the adhesive layer.
[0078] This method is effective against not only variations in
luminance, but also variations in color saturation, since the
thickness of the adhesive layer is not varied in a surface and, in
addition, toning can be performed on a formulation basis. In this
method as well, the above-described film formation method can be
used. For example, as for the T die method, when the supply of
material is divided into three before extrusion, and the resulting
three components are put in so that the total light transmittances
become large-medium-small from the end, a film of the adhesive
having a large-medium-small total light transmittance after film
formation can be formed. When the resulting three components are
put in so that the total light transmittances become
small-large-small, a film of the adhesive having a
small-large-small total light transmittance after film formation
can be formed. The same holds true for the comma method. The total
light transmittance and the quantity of supply of each material are
controlled and, thereby, an adhesive having a total light
transmittance being continuously varied in one desired direction
can be produced. Since this method can independently change the
toning of each material, an adhesive layer having not only a total
light transmittance being continuously varied, but also a color
saturation being continuously varied, can be produced.
[0079] In the above-described embodiment, the total light
transmittance of the adhesive layer is varied and, thereby, the
total light transmittance of the film is varied in a
one-dimensional direction or a two-dimensional direction. However,
in the present invention, the total light transmittance of the film
may also be varied in a one-dimensional direction or a
two-dimensional direction by varying the total light transmittance
of the base film itself. In order to realize this, it is essential
that the content of coloring matter or pigment in the film is made
to have a distribution in the one-dimensional direction or the
two-dimensional direction during film formation. This coloring
matter or pigment may be, for example, the above-described coloring
matter or pigment to be contained in the adhesive. Alternatively,
the concentration of the coloring matter or pigment in the base
film may be kept constant, and the total light transmittance of the
film may be varied in a one-dimensional direction or a
two-dimensional direction by varying the thickness of the base
film.
[0080] In the present invention, a colored layer different from the
adhesive layer may be disposed on the surface of the base film, and
the total light transmittance of the film may be varied in a
one-dimensional direction or a two-dimensional direction by varying
the thickness or the color strength of this colored layer. This
colored layer may be disposed only for the purpose of varying the
total light transmittance, or may also serves as a functional
layer, e.g., an antireflection layer, an antiglare layer, a hard
coat layer, or an electrically conductive layer. When this colored
layer is formed, preferably, a printing material containing a
coloring matter or a pigment, is printed. This coloring matter or
pigment may be similar to that contained in the above-described
adhesive layer.
[0081] The present invention will be more specifically described
below with reference to examples and comparative examples. However,
the present invention is not limited to the following examples, and
covers various modifications and the like included within the scope
of the present invention.
EXAMPLE 1
[0082] A flask was provided with a thermometer, an agitator, a
reflux cooling pipe, and a nitrogen introduction pipe, and 68 parts
by weight of n-butyl acrylate, 22 parts by weight of methyl
acrylate, 10 parts by weight of acrylic acid, 0.1 parts by weight
of azobisisobutylonitrile, 40 parts by weight of ethyl acetate, and
60 parts by weight of toluene were put therein. Nitrogen was
introduced through the nitrogen introduction pipe and, thereby, the
inside of the flask was brought into a nitrogen atmosphere.
Thereafter, the resulting mixture was heated to 65.degree. C. and a
polymerization reaction was performed for 10 hours, so that an
acrylic polymer solution having a weight average molecular weight
of about 350,000 and Tg of about -25.degree. C. was produced. Ethyl
acetate was added to the acrylic polymer solution so that the
solids content became 28 percent by weight and, therefore, a
polymer solution A was produced.
[0083] A coating solution was prepared by blending 100 parts by
weight of polymer solution A with 0.05 parts by weight of epoxy
cross-linking agent (trimethylolpropane triglycidyl ether) and 2
parts by weight of pigment (CAB LX905 Black produced by TOYO INK
MFG. CO., LTD.). The resulting coating solution was applied to a
mold release PET film "DIAFOIL MRF38" (produced by Mitsubishi
Polyester Film Corp.) having been subjected to a silicone treatment
and having a thickness of 38 .mu.m in a manner as shown in FIGS. 4A
and 4B, followed by drying. The same coating solution as the
above-described coating solution except that no pigment was
included was further applied thereon, followed by drying.
Furthermore, a PET film "OLW" (produced by Teijin DuPont Films
Japan Limited) having a thickness of 175 .mu.m was stuck
thereon.
[0084] In this manner, an adhesive-layer-including film having the
sectional configuration shown in FIG. 1 (although the
antireflection layer 6 is not shown) was produced.
[0085] The thickness of the central portion of the adhesive layer 3
was 20 .mu.m, and the thicknesses of both end sides of the film
were 10 .mu.m. The total thickness of the adhesive layer 3 and the
adhesive layer 4 was 25 .mu.m (constant).
[0086] The mold release PET film was peeled off this film. The
resulting film was stuck to glass having a thickness of 3 mm, and
the total light transmittance was measured. As a result, the total
light transmittance of the film was 50% at the center in the width
direction, and was 70% at both end sides.
[0087] As described above, according to the present invention, a
film having a total light transmittance being varied in the film
width direction is provided.
[0088] II. The embodiments of a dimmer film of the present
invention and a manufacturing method therefor will be described
below in detail with reference to FIGS. 9A to 9E.
[0089] In the production of the dimmer film, a colored layer 42
containing a dye which tends to be faded due to ultraviolet light B
and has excellent heat resistance (hereafter may be referred to as
"an easy-to-fade dye") is formed on a base film 41 (FIGS. 9A and
9B).
[0090] Examples of materials for this base film 41 include
cellulose films of triacetyl cellulose base; polycarbonate films;
polyester films, e.g., polyethylene terephthalate; and polyolefin
films, e.g., polyethylene and polypropylene, although not limited
to them. Preferably, the thickness of the base film 41 is
controlled at within the range of 25 to 250 .mu.m since
satisfactory strength is attained and the thickness of the dimmer
film is not excessively increased.
[0091] The easy-to-fade dye to be blended into the colored layer 42
is not specifically limited. For example, "Kayaset Black G" and
"Kayaset Black B" produced by Nippon Kayaku Co., Ltd., "Oil
Colours", "Black 141", and "Oil Colours Black 6" produced by CHUO
SYNTHETIC CHEMICAL CO., LTD., and the like can be used.
[0092] Preferably, the colored layer 42 is an adhesive layer.
Previously known various adhesives of, e.g., rubber base, acryl
base, silicone base, and EVA (ethylene-vinyl acetate) base, can be
used as the adhesive to form the colored adhesive layer.
[0093] The content of the easy-to-fade dye in the colored layer 42,
e.g., a colored adhesive layer, is not specifically limited.
However, about 0.1 to 20 percent by weight is preferable. If the
content of the easy-to-fade dye in the colored layer 42 is smaller
than the above-described range, it is difficult to provide the
colored layer with significant changes in color strength by fading
through application of the ultraviolet light B. If the content of
the easy-to-fade dye is larger than the above-described range, the
film formation property and the like of the colored layer is
deteriorated.
[0094] The thickness of this colored layer 42 is not specifically
limited. However, about 0.01 to 30 .mu.m is preferable. This is
because if the thickness of this colored layer 42 is smaller than
the above-described range, it is difficult to provide the colored
layer with significant changes in color strength by fading through
irradiation of the ultraviolet light B, and if the thickness of the
colored layer 42 is larger than the above-described range, the
thickness of the dimmer film is increased, and the fading becomes
unsatisfactory.
[0095] This colored layer 42 can be formed by applying a
predetermined thickness of adhesive composition containing a
predetermined quantity of easy-to-fade dye to the base film.
[0096] The coating method is not specifically limited. Examples
thereof can include a gravure coater, a bar coater, a roll coater,
a knife coater, and a reverse roll coater. Preferably, the gravure
coating method is adopted since the uniformity of the thickness is
required.
[0097] This colored layer 42 is formed on the base film 41 with a
uniform thickness and with uniform color strength.
[0098] After the colored layer 42 is formed, the colored layer 42
is irradiated with the ultraviolet light B through a mask 43 having
an ultraviolet light B transmission quantity distribution in the
surface direction and, thereby, the colored layer 42 is faded so
that the color strength is varied in the surface direction (FIG.
9C).
[0099] In FIG. 9C, the mask 43 made of PET film is used. The
thickness of the central portion of the mask 43 is larger than the
thicknesses of both end portions, and the thickness is continuously
varied from the central portion toward both end portions. As a
result, the light transmission quantity is continuously decreased
from the central portion toward both end portions so that the
ultraviolet light B transmission quantity is decreased at the
central portion and the ultraviolet light B transmission quantity
is increased at both end portions.
[0100] The thickness of this mask 43 is appropriately determined in
accordance with the irradiation quantity of light required for
fading the colored layer 42. In general, the ultraviolet light B
(310 nm) transmission quantity of the PET film is about 20% when
the thickness is 10 .mu.m, and is about 4.4% when the thickness is
20 .mu.m. Consequently, the mask 43 is appropriately designed so
that a predetermined light transmission quantity can be attained at
a predetermined portion while the thickness is within the range of
5 to 30 .mu.m.
[0101] The mask 43 shown in FIG. 9C can be produced by, for
example, performing extrusion while a blade having an arch surface
curved to become convex upward in the width direction is disposed
at an extrusion hole in the extrusion of the film. Alternatively,
the mask 43 can be produced by stacking and integrating very thin
films, which are molded beforehand and have different areas, at
predetermined portions so that predetermined thicknesses are
attained.
[0102] The material for the mask is not limited to PET. It is
essential only that the material for the mask has excellent
ultraviolet light B resistance and the ultraviolet light B
transmission quantity can be controlled. Quartz glass,
fluororesins, and other resinous materials may be used. The
material for the mask is not limited to the material in which the
ultraviolet light B transmission quantity is varied by changing the
thickness, and may be a material in which the ultraviolet light B
transmission quantity is varied by changing the ultraviolet light B
absorptive power in the surface direction of the mask.
[0103] The ultraviolet light B (wavelength 280 to 315 nm) can be
applied through the above-described mask 43 by using a general
ultraviolet light B lamp or metal halide lamp. Preferably, the
output of this ultraviolet light B is about 80 to 300 W/cm from the
viewpoint of the effect on fading the colored layer 42. However,
the degree of fading of the colored layer 42 due to the ultraviolet
light B is different depending on the application time of the
ultraviolet light B and the distance between the colored layer and
the lamp. Therefore, preferably, these conditions, as well as the
output, are set appropriately.
[0104] In this manner, the easy-to-fade dye in the colored layer 42
is faded by applying the ultraviolet light B to the colored layer
42 through the mask 43 and, thereby, the color strength of the
colored layer 42 is varied in the surface direction thereof.
[0105] In the case where the mask 43 shown in FIG. 9C is used, the
quantity of application of the ultraviolet light B is small at the
central portion of the colored layer 42, and the quantity of
application of the ultraviolet light B is large at both end
portions. As a result, the color strength of the colored layer 42A
after being faded is continuously varied from the center toward
both end portions so that the color strength is high at the central
portion and the color strength is low at both end portions (FIG.
9D).
[0106] After the colored layer 42 is faded as described above, an
adhesive layer 44 containing a pigment is formed on this faded
colored layer 42A. The adhesive layer may be formed on the surface
opposite to the colored layer of the base film.
[0107] Previously known various adhesives of, e.g., rubber base,
acryl base, silicone base, and EVA base, can be used as the
adhesive to form this adhesive layer 44. Examples of pigments
include inorganic pigments, e.g., carbon black, titanium oxide,
chromium oxide, oxide yellow, red ion oxide, and ultramarine, and
organic pigments, e.g., azo pigments, phthalocyanine pigments,
anthracene pigments, threne pigments, and dioxazine pigments,
although not limited to them.
[0108] The content of the pigment in the adhesive layer 44 is not
specifically limited. However, about 0.01 to 10 percent by weight
is preferable. If the content of the pigment in the adhesive layer
44 is smaller than the above-described range, the effect on
adjusting the transmitted color due to disposition of this adhesive
layer 44 cannot be satisfactorily exerted. If the content of the
pigment is larger than the above-described range, the film
formation property and the like of the adhesive layer is
deteriorated and, in addition, satisfactory adhesion cannot be
attained.
[0109] The thickness of this adhesive layer 44 is not specifically
limited. However, 5 to 50 .mu.m is preferable. If the thickness of
the adhesive layer 44 is smaller than the above-described range,
the effect on adjusting the transmitted color due to disposition of
this adhesive layer 44 cannot be adequately exerted. If the
thickness of the adhesive layer 44 is larger than the
above-described range, the thickness of the dimmer film is
increased, and the productivity is deteriorated.
[0110] This adhesive layer 44 can be formed by applying a
predetermined thickness of adhesive composition containing a
predetermined quantity of pigment on the colored layer 42 or on the
side opposite thereto. The coating method therefor is not
specifically limited. Although a method similar to the coating
method for the colored layer 42 can be adopted, a knife coater
method is preferable since the viscosity of the coating solution is
high.
[0111] Preferably, this adhesive layer 44 is formed on the colored
layer 42 with a uniform thickness and with uniform color strength
as well.
[0112] Usually, a mold release film is stuck to this adhesive layer
44. The material for this mold release film is similar to that for
the above-described base film 41, and the thickness thereof is
usually about 25 to 100 .mu.m.
[0113] The thus produced dimmer film is most highly colored (the
total light transmittance is low.) at the central portion, and
becomes lightly colored with increasing proximity to both end
sides. That is, the total light transmittance of the dimmer film is
increased with increasing proximity to both end sides.
[0114] Consequently, in the case where the mold release film is
peeled off and the dimmer film is stuck to a display, when
variations in luminance of the display is in a pattern reverse to
the distribution of light and dark of the dimmer film, the
variations in luminance can be eliminated or reduced.
[0115] In the present invention, the dimmer film is basically
composed of the base film 41, the faded colored layer 42A,
preferably faded colored adhesive layer, and the adhesive layer 44,
as shown in FIG. 9E. However, the mold release film may be disposed
on the adhesive layer 44, as described above. An antireflection
layer may be disposed on the surface opposite to the surface
provided with the colored layer of the base film. In this case,
preferably, the thickness of the antireflection layer is about 0.1
to 10 .mu.m. The antireflection layer may be formed before the
colored layer is formed. In addition, a hard coat layer, an
electrically conductive layer, an antiglare layer, and the like may
be included. The colored layer may also serve as these functional
layers.
[0116] According to the present invention, for example, a film
exhibiting a percentage a/b.times.100% of the total light
transmittance a at the center relative to the total light
transmittance b on both end sides of about 10% to 95% can be
provided. The total light transmittance of this dimmer film may be
varied one-dimensionally or two-dimensionally in the film surface
direction. The design of the total light transmittance of the
dimmer film can be arbitrarily changed by selecting the mask.
[0117] As for the dimmer film of the present invention, the colored
layer disposed on the base film and containing the easy-to-fade dye
is irradiated with the ultraviolet light B having a light quantity
distribution in the surface direction so that the colored layer is
faded and the color strength is varied in the surface direction.
The adhesive layer containing the pigment is disposed and, thereby,
the transmitted color of the faded colored layer is adjusted. The
method for manufacturing the dimmer film is not limited to the
method shown in FIGS. 9A to 9E.
[0118] For example, as shown in FIGS. 9A to 9C, the colored layer
42 containing the easy-to-fade dye is formed on the base film 41,
the ultraviolet light B is applied through the mask 43 and,
thereafter, the adhesive layer containing the pigment and disposed
on the mold release film is stuck thereto, so that the dimmer film
can be produced as well. Alternatively, it is also possible to form
the colored layer and the adhesive layer on the base film and,
thereafter, fade the colored layer by applying the ultraviolet
light B through the mask, as shown in FIG. 9C. However, it is
preferable to adopt the manufacturing method shown in FIGS. 9A to
9E on the ground that the state of fading of the colored layer is
ascertained and, thereafter, the adhesive layer containing the
pigment can be formed so that a desired transmitted color is
attained.
[0119] An example of adhesives suitable for use in the dimmer film
of the present invention is an adhesive containing a (meth)acrylic
resin as a primary component and an epoxy compound as a
cross-linking agent, wherein the (meth)acrylic resin contains 1 to
25 percent by weight of monomer component having a carboxyl group,
as a copolymerization component of the alkyl(meth)acrylate.
[0120] This adhesive is the same as the adhesive used in the
adhesive layer 73 which will be described below with reference to
FIG. 10.
[0121] The dimmer film of the present invention and the
manufacturing method therefor will be more specifically described
below with reference to examples and comparative examples. However,
the present invention is not limited to the following examples, and
covers various modifications and the like included within the scope
of the present invention.
EXAMPLE 2
[0122] A dimmer film was produced by the method shown in FIGS. 9A
to 9E.
[0123] A colored adhesive layer (thickness 8 .mu.m) made of an
acrylic adhesive ("Foret M-80" produced by Soken Chemical and
Engineering Co., Ltd.) containing 5 percent by weight of an
easy-to-fade dye, "Kayaset Black G" produced by Nippon Kayaku Co.,
Ltd., was formed by a gravure coating method on the surface of
"O300" (thickness 100 .mu.m) produced by Mitsubishi Polyester Film
Corp., serving as the base film.
[0124] This colored adhesive layer is irradiated with the
ultraviolet light B (output 80 W/cm) from a UV-B lamp "TL/12 lamp"
produced by Philips Japan Ltd., at a distance of 40 cm for 60
minutes through the following mask and, thereby, the colored
adhesive layer was faded.
[0125] Mask
[0126] A mask in which the thickness of the central portion was 25
.mu.m, the thicknesses of both end portions were 60 .mu.m, and the
thickness was continuously varied from the central portion toward
both end portions.
[0127] Subsequently, an adhesive layer (thickness 25 .mu.m) was
formed on the faded colored adhesive layer by using an acrylic
adhesive ("2065M" produced by Soken Chemical and Engineering Co.,
Ltd.) containing 0.1 percent by weight of "CAB LX905" and 0.4
percent by weight of "CAB LX716", each produced by TOYO INK MFG.
CO., LTD., as a pigment.
[0128] The total light transmittance and the transmitted color of
the thus produced dimmer film are shown in Table 1. A desired
transmitted color was attained.
COMPARATIVE EXAMPLE 1
[0129] A colored adhesive layer and an adhesive layer were formed
as in Example 1 except that the ultraviolet light B was not
applied. The total light transmittance and the transmitted color of
the resulting film are shown in Table 1.
COMPARATIVE EXAMPLE 2
[0130] A dimmer film was formed as in Example 1 except that the
adhesive layer was not formed. The total light transmittance of the
resulting film is shown in Table 1. The transmitted color was
yellow and, therefore, any desired transmitted color was not
attained.
1TABLE 1 Total light transmittance Transmitted color Example 2
central portion: 67%, both gray, desired transmitted end portions:
85%, varying color continuously Comparative 65%, uniform gray
example 1 Comparative central portion: 70%, both central portion:
gray, both example 2 end portions: 91%, varying end portions:
yellow, continuously undesired transmitted color
[0131] The dimmer film of the present invention can be effectively
applied to liquid crystal displays of back light system or front
light system, other displays, e.g., CRT, PDP, and FED, and in
addition, display panels, e.g., electric bulletin boards, having
light sources.
[0132] III. The embodiments of a display adhesive and a display
functional film will be described below in detail with reference to
FIG. 10. FIG. 10 is a sectional view showing an embodiment of a
display functional film according to the present invention.
[0133] In a display functional film 71, an adhesive layer 73 made
of the adhesive according to the present invention is disposed on
one surface of a base film 72, a functional layer 74, e.g., a hard
coat layer, an electrically conductive layer, an antiglare layer,
or an antireflection layer, is disposed on the other surface, and a
mold release film 75 is disposed on the adhesive layer 73.
[0134] The display adhesive of the present invention, used for the
above-described display functional film 71 of the present invention
will be described below.
[0135] The display adhesive of the present invention contains a
(meth)acrylic resin as a primary component and an epoxy compound as
a cross-linking agent, wherein the (meth)acrylic resin contains 1
to 25 percent by weight of monomer component having a carboxyl
group, as a copolymerization component of the
alkyl(meth)acrylate.
[0136] Examples of alkyl(meth)acrylates constituting the
(meth)acrylic resin according to the present invention include
alkyl esters of acrylic acid or methacrylic acid having an alkyl
group, e.g., a methyl group, an ethyl group, an isopropyl group, a
n-butyl group, an isobutyl group, an isoamyl group, a hexyl group,
a heptyl group, a cyclohexyl group, a 2-ethylhexyl group, an
isooctyl group, an isononyl group, a lauryl group, a dodecyl group,
an isomyristyl group, and an octadecyl group. These may be used
alone or in combination.
[0137] Examples of monomer components having a carboxyl group
include (meth)acrylic acid; carboxyalkyl(meth)acrylates, e.g.,
carboxyethyl(meth)acrylate and carboxypentyl(meth)acrylate;
itaconic acid; maleic acid; and crotonic acid. These may be used
alone or in combination.
[0138] The (meth)acrylic resin may contain other copolymerization
components in addition to the above-described alkyl(meth)acrylate
and a monomer component having a carboxyl group. Examples of other
usable copolymerization components include maleimide monomers,
e.g., N-cyclohexylmaleimide, N-isopropylmaleimide,
N-laurylmaleimide, and N-phenylmaleimide; itaconimide monomers,
e.g., N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide,
N-octylitaconimide, N-2-ethylhexylitaconimide,
N-cyclohexylitaconimide, and N-laurylitaconimide; succinimide
monomers, e.g., N-(meth)acryloyloxymethy- lenesuccinimide,
N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and
N-(meth)acryloyl-8-oxyoctamethylenesuccinimide;
sulfonic-acid-containing monomers, e.g.,
2-acrylamide-2-methylpropanesulfonic acid;
phosphoric-acid-containing monomers, e.g.,
2-hydroxyethylacryloylphosphat- e; vinyl monomers, e.g., vinyl
acetate and styrene; divinyl monomers, e.g., divinylbenzene;
diacrylate monomers, e.g., 1,4-butyl diacrylate and 1,6-hexyl
diacrylate; acrylic acid ester monomers, e.g.,
tetrahydrofurfuryl(meth)acrylate, polyethylene
glycol(meth)acrylate, polypropylene glycol(meth)acrylate,
fluorinated (meth)acrylate, and silicone(meth)acrylate;
alkoxy-containing monomers, e.g., trimethoxysilylpropyl acrylate;
acid anhydride monomers, e.g., maleic anhydride and itaconic
anhydride; and other compounds, e.g., hexanediol di(meth)acrylate,
(poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol
di(meth)acrylate, neopentylglycol di(meth)acrylate, pentaerythritol
di(meth)acrylate, trimethylolpropane tri(meth)acrylate,
pentaerythritol tri(meth)acrylate, dipentaerythritol
hexa(meth)acrylate, epoxy acrylate, polyester acrylate, and
urethane acrylate.
[0139] Monomer components having a functional group other than the
carboxylic group can also be used. Examples of monomers having a
functional group include hydroxyl-containing monomers, e.g.,
2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,
4-hydroxybutyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate,
8-hydroxyoctyl(meth)acrylate, 10-hydroxydecyl(meth)acrylate,
12-hydroxylauryl(meth)acrylate, and
(4-hydroxymethylcyclohexyl)-methyl acrylate; epoxy-containing
monomers, e.g., glycidyl (meth)acrylate; and amide monomers, e.g.,
(meth)acrylamide, N-acryloylmorpholine, N-substituted
(meth)acrylamide, and N-vinylpyrrolidone.
[0140] If the content of monomer component containing a carboxyl
group in the (meth)acrylic resin is smaller than 1 percent by
weight, the adhesion to a display panel made of, e.g., glass, is
lowered. If the content exceeds 25 percent by weight, the glass
transition temperature Tg of the adhesive tends to be increased, so
that satisfactory tackiness cannot be attained. Therefore, it is
preferable that the content of monomer component containing a
carboxyl group is 1 to 25 percent by weight, in particular, 5 to 20
percent by weight.
[0141] Preferably, the content of alkyl(meth)acrylate which is a
primary component of the (meth)acrylic resin is 50 percent by
weight or more, in particular, 60 percent by weight or more in
order to ensure the optical properties as the (meth)acrylic
resin.
[0142] The (meth)acrylic resin according to the present invention
is produced from an alkyl(meth)acrylate, a monomer component having
a carboxyl group, and other copolymerization components used as
required by polymerizing these monomer components through a common
polymerization system, e.g., solution polymerization, emulsion
polymerization, bulk polymerization, or suspension polymerization.
In this polymerization, a thermal polymerization initiator or a
photopolymerization initiator is used. Alternatively, potassium
persulfate, ammonium persulfate, hydrogen peroxide, a redox
initiator in which the above-described compound and a reducing
agent are used in combination, or the like is used.
[0143] Among the polymerization initiators, examples of thermal
polymerization initiators include organic peroxides, e.g., benzoyl
peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl
peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl)
peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl
peroxypivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl
peroxide, and diacetyl peroxide; and azo compounds, e.g.,
2,2'-azobisisobutylonitrile, 2,2'-azobis(2-methylbutylonitrile),
1,1'-azobis(cyclohexane-1-carbonitril- e),
2,2'-azobis(2,4-dimethylvaleronitrile),
2,2'-azobis(2,4-dimethyl-4-met- hoxyvaleronitrile),
dimethyl-2,2'-azobis(2-methylpropionate),
4,4'-azobis(4-cyanovaleric acid),
2,2'-azobis(2-hydroxymethylpropionitril- e), and
2,2'-azobis[2-(2-imidazoline-2-yl)propane].
[0144] Examples of photopolymerization initiators include
acetophenone initiators, e.g., 4-(2-hydroxyethoxy)phenyl(2
-hydroxy-2-propyl) ketone,
.alpha.-hydroxy-.alpha.,.alpha.'-dimethylacetophenone,
methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone,
1-hydroxycyclohexylphenyl ketone, and
2-methyl-1-[4-(methylthio)-phenyl]-- 2-morpholinopropane-1; benzoin
ether initiators, e.g., benzoyl ethyl ether and benzoin isopropyl
ether; ketal initiators, e.g., benzyl methyl ketal; benzophenone
initiators, e.g., benzophenone, benzoylbenzoic acid, and
3,3'-dimethyl-4-methoxybenzophenone; and thioxanthone initiators,
e.g., thioxanthone, 2-chlorothioxane, 2-methylthioxanthone,
2,4-dimethylthioxanthone, isopropylthioxanthone,
2,4-dicyclothioxanthone, 2,4-diethylthioxanthone, and
2,4-diisopropylthioxanthone. In addition, camphorquinone,
halogenated ketone, acylphosphinoxide, acylphosphonate, and the
like can also be used.
[0145] The usage of the polymerization initiator is not
specifically limited. However, preferably, the usage is usually
0.001 to 5 percent by weight relative to the monomer component to
be used.
[0146] Preferably, the weight average molecular weight of the
(meth)acrylic resin is 500,000 to 2,000,000. If the weight average
molecular weight of the (meth)acrylic resin is smaller than
500,000, the heat resistance to 120.degree. C. or more is
deteriorated. If the weight average molecular weight exceeds
2,000,000, the synthesis takes significantly much time and, in
addition, the viscosity of the adhesive solution becomes very high,
so that the productivity, e.g., the workability of coating, is
deteriorated.
[0147] The cross-linking agent contained in the adhesive is an
epoxy compound. The epoxy cross-linking agent may be ethylene
glycol diglycidyl ether, propylene glycol diglycidyl ether,
diglycidyl ether, trimethylolpropane triglycidyl ether, or the
like. These may be used alone or in combination.
[0148] If the content of the epoxy cross-linking agent is too
small, the effect on improving the adhesion due to compounding the
epoxy cross-linking agent is not satisfactorily exerted. If the
content is too large, significant shrinkage is effected by
cross-linking and, thereby, the film may be warped. Therefore, it
is preferable that the content is 0.5 to 50 percent by weight
relative to the monomer component having a carboxyl group in the
(meth)acrylic resin.
[0149] Cross-linking agents other than the epoxy cross-linking
agent may be contained. Examples of the above-described
cross-linking agents include multifunctional isocyanate
cross-linking agents, e.g., tolylene diisocyanate,
trimethylolpropane tolylene diisocyanate, and diphenylmethane
tolylene diisocyanate; melamine resin cross-linking agents; metal
salt cross-linking agents; metal chelate cross-linking agents, and
amino resin cross-linking agents. Preferably, the total content of
the above-described epoxy cross-linking agent and the cross-linking
agents other than the epoxy cross-linking agent is 10 percent by
weight or less relative to the (meth)acrylic resin.
[0150] With respect to some displays which have been developed in
recent years, the hue, the lightness, and the color saturation of
the light from the display are adjusted by functional light
transmission films. In some cases, adhesive layers are provided
with this adjustment function. Therefore, a dye or pigment can be
added to the adhesive of the present invention in order to provide
such a function. The pigment is used preferably as compared with
the dye from the viewpoint of the durability. Examples of pigments
having excellent compatibility with the adhesive of the present
invention include CAB pigments produced by TOYO INK MFG. CO., LTD.
It is possible to perform desired toning by using them alone or in
combination. The adhesive of the present invention may be blended
with additives, e.g., ultraviolet absorbers, conductivity-imparting
agents, oxidation inhibitors, antioxidants, natural and synthetic
resins, glass fibers, and glass beads within the range in which the
transparency is not impaired. Fine particles may be blended to
provide the adhesive with the light diffusion property.
[0151] In order to form the adhesive layer 73 of the display
functional film 71, for example, a (meth)acrylic resin as a primary
component of the adhesive may be dissolved or dispersed in an
appropriate organic solvent, e.g., toluene and ethyl acetate, so as
to prepare a solution containing about 10 to 40 percent by weight
of adhesive, an epoxy cross-linking agent may be further added
thereto, followed by agitating. Thereafter, the resulting solution
may be applied by a flow casting method or a coating method to one
surface of the base film 72, followed by drying. Alternatively, the
above-described solution containing the adhesive may be applied to
a separator (mold release film 75), and be dried so as to form the
adhesive layer 73. Subsequently, this may be stuck to the base film
72.
[0152] The thickness of the adhesive layer 73 disposed in the
display functional film 71 is not specifically limited. However, in
general, it is preferable that the adhesive layer 73 is formed to
have a thickness of about 5 to 50 .mu.m.
[0153] The base film 72 of the display functional film 71 is not
specifically limited. However, a base film having optical
transparency is used preferably. Examples of preferable films used
as the base film include cellulose films made of, e.g., triacetyl
cellulose; polycarbonate films; polyester films made of, e.g.,
polyethylene terephthalate (PET); and polyolefin films made of,
e.g., polyethylene and polypropylene, from the viewpoint of optical
properties, strength, economy, and the like. In general, it is
preferable that the thickness thereof is about 30 to 300 .mu.m from
the viewpoint of the strength, reduction in thickness, and the
like.
[0154] Examples of functional layers 74 to be disposed on the base
film 72 include at least one of a hard coat layer, a transparent
electrically conductive layer, an antiglare layer, an
antireflection layer, and the like, although not limited to
them.
[0155] A hard sheet, e.g., a glass sheet, an acrylic sheet, or a
polycarbonate sheet, having a thickness of about 1 to 10 mm is used
as a display panel to which the display functional film is stuck.
However, the material and the thickness are not specifically
limited.
[0156] The adhesive and the display film of the present invention
will be more specifically described below with reference to
examples and comparative examples. However, the present invention
is not limited to the following examples, and covers various
modifications and the like included within the scope of the present
invention.
EXAMPLE 3
[0157] A flask was provided with a thermometer, an agitator, a
reflux cooling pipe, and a nitrogen introduction pipe, and 68 parts
by weight of n-butyl acrylate, 22 parts by weight of methyl
acrylate, 10 parts by weight of acrylic acid, 0.1 parts by weight
of azobisisobutylonitrile, 40 parts by weight of ethyl acetate, and
60 parts by weight of toluene were put therein. Nitrogen was
introduced through the nitrogen introduction pipe and, thereby, the
inside of the flask was brought into a nitrogen atmosphere.
Thereafter, the resulting mixture was heated to 65.degree. C. and a
polymerization reaction was performed for 10 hours, so that an
acrylic polymer solution having a weight average molecular weight
of about 350,000 and Tg of about -25.degree. C. was produced. Ethyl
acetate was added to the acrylic polymer solution so that the
solids content became 28 percent by weight and, therefore, a
polymer solution A was produced.
[0158] A coating solution was prepared by blending 100 parts by
weight of polymer solution A with 0.05 parts by weight of epoxy
cross-linking agent (trimethylolpropane triglycidyl ether). The
resulting coating solution was applied to a mold release PET film
"DIAFOIL MRF38" (produced by Mitsubishi Polyester Film Corp.)
having been subjected to a silicone treatment and having a
thickness of 38 .mu.m, followed by drying. A PET film "OLW"
(produced by Teijin DuPont Films Japan Limited) having a thickness
of 175 .mu.m was stuck thereto.
[0159] The mold release PET film was peeled off this film. The
resulting film was stuck to glass having a thickness of 3 mm to
prepare a measurement sample. The adhesion and the degree of
discoloration were evaluated by the following methods. The results
are shown in Table 2.
[0160] <Adhesion>
[0161] The above-described measurement sample was stood for 500
hours in an atmosphere at a temperature and a humidity shown in
Table 2 and, thereafter, the adhesion relative to 180-degree
peeling was measured in conformance with JIS Z-0237.
[0162] <Degree of Discoloration>
[0163] The above-described measurement sample was stood for 500
hours in an atmosphere at a temperature and a humidity shown in
Table 2 and, thereafter, the color difference .DELTA.E from the
initial state with a two-degree-field D65 light source was measured
in conformance with JIS Z-8730.
COMPARATIVE EXAMPLE 3
[0164] The polymerization reaction was performed as in Example 3
except that 65 parts by weight of n-butyl acrylate, 20 parts by
weight of methyl acrylate, 15 parts by weight of acrylic
acid-2-hydroxyethyl ester, 0.1 parts by weight of
azobisisobutylonitrile, 40 parts by weight of ethyl acetate, and 60
parts by weight of toluene were put in the flask, so that an
acrylic polymer solution having a weight average molecular weight
of about 750,000 and Tg of about -23.degree. C. was produced. Ethyl
acetate was added to the acrylic polymer solution so that the
solids content became 28 percent by weight and, therefore, a
polymer solution B was produced.
[0165] An adhesive layer was formed as in Example 3 except that 0.1
parts by weight of tolylene diisocyanate was added to 100 parts by
weight of this polymer solution B. The adhesion and the degree of
discoloration were evaluated as in the above description. The
results are shown in Table 2.
2 TABLE 2 Atmosphere Temperature Humidity Comparative (.degree. C.)
(% RH) Example 3 example 3 Adhesion 23 40 3000 2000 (gf/25 mm) 100
Dry 3300 2300 120 Dry 3300 700 60 90 3000 100 Degree of 100 Dry
0.22 0.72 discoloration 120 Dry 0.71 2.40 (.DELTA.E)
[0166] As is clear from Table 2, the adhesive of the present
invention has high adhesion, and the adhesion and the optical
properties exhibit excellent high-temperature durability and
high-humidity durability.
[0167] As described above in detail, the display adhesive of the
present invention has high adhesion to a display panel and the
adhesion and the optical properties exhibit excellent
high-temperature durability and high-humidity durability.
Consequently, the display functional film of the present invention
provided with the adhesive layer made of the display adhesive of
the present invention can stably maintain excellent adhesion and
transparency for the long term without occurrence of deterioration,
e.g., peeling and yellowing, in the use for various electronic
display panels.
* * * * *